Polarised electromagnetic relays and like devices



Dec. 17, 1957 R. E. H. CARPENTER POLARISED ELECTROMAGNETIC RELAYS ANDLIKE DEVICES 4 Sheets-Sheet 1 Filed July 8, 1955 flgZ J3 35 5456374 7 Hwlll I l l I F l I I l L J I 47 1/ 55 ffl Inventor By '79, 4 17M 2Attorney 4 Sheets-Sheet 2 R. E. H. CARPENTER POLARISED ELECTROMAGNETICRELAYS AND LIKE DEVICES Filed July 8, 1955 Dc. 17, 1957 R. E. H.CARPENTER 2,816,976

POLARISED ELECTROMAGNETIC RELAYS AND LIKE DEVICES Filed July 8, 1955 v 4Sheets-Sheet 3 I n uenlor BYWQM A Home y 4 Sheets-Sheet 4 lllllnllllllllvl R. E. H. CARPENTER l I o 0 POLARISED ELECTROMAGNETIC RELAYS AND LIKEDEVICES Filed July 8, 1955 'DecQ 17, 1957 I Inventor Wm M y W417.-AUorney United States Patent POLARISED ELECTROMAGNETIC RELAYS AND LIKEDEVICES Rupert E. H. Carpenter, South Croydon, England Application July8, 1955, Serial No. 520,853

13 Claims. (Cl. 200-93) This invention relates to polarisedelectromagnetic instruments, such as polarised electromagnetic relaysand polarised telephone indicators, having a magnetic circuit which islinked with the operating or signals winding of the instrument and whichincludes opposed pole-faces, with the armature pivoted in the gapbetween these polefaces so as to be able to rock to and from them toproduce a change in the lengths of the air gaps between the armature andthe pole-faces.

In such instruments, the operating or signals flux flows from onepole-face to the other through the armature. Since, however, the latterhas hitherto always consisted solely of the permanent magnet whichproduces the polarising flux, and since permanent magnetic alloys havesmall permeability, this armature introduced into the operating orsignals magnetic circuit an undesirable reluctance, and this caused suchinstruments to have low efficiency.

The object of the present invention is to provide an instrument having amuch greater efliciency than those used hitherto.

Thus, according to the invention, at least a part of the armaturecomprises a member of magnetically soft material, such as soft iron,which receives polarising flux directly from a permanent magnet andwhich serves as a bridge of low reluctance to carry operating or signalsflux across the gap between the pole-faces. This reduction in thereluctance in the operating or signals magnetic circuit then causes anincrease in the operating or signals flux and this leads to an increasein the efficiency of the instrument.

In the preferred form of a relay constructed according to the invention,the armature consists of the polarising magnet and two members ofmagnetically soft material fixed to it, one at either end. In anotherform, however, the polarising magnet is stationary and the members ofmagnetically soft material are then connected together and pivotallymounted to act as the armature.

Preferably the armature is substantially enclosed within a housing orbox which is made up in part of the polefaces and two parallel spacingmembers extending along adjacent sides of the two pole-faces and actingto maintain them a fixed distance apart and on which the contactassembly of the relay is mounted. This enclosure thus substantiallyprevents the ingress of magnetic and other particles particularly duringmanufacture.

Two examples of polarised electromagnetic relays constructed accordingto the invention will now be described with reference to theaccompanying drawings, in which:

Figure 1 is a side elevation of the first example, partly broken away toshow the major part of the armature;

Figure 2 is a corresponding front elevation partly broken away to showpart of the plates which constitute the pole-faces, and showing indotted lines the rest of the plates and the armature between them;

Figure 3 is a diagrammatic view of the polarising and signals magneticcircuits of either of the two examples;

Figure 4 is a side elevation mainly in section, of the pivotingarrangement of the armature of either of the two examples;

Figure 5 is the front elevation corresponding to Figure 4;

Figure 6 is a plan view of the contact assembly of either of the twoexamples;

Figure 7 is a side elevation of the second example, and corresponds toFigure 1;

Figure 8 is the front elevation corresponding to Figure 7 and thuscorresponds to Figure 2; and

Figure 9 shows an alternative method of pivoting the armature.

Referring first of all to Figures 1 and 2, the signals magneticstructure includes two signal coils l and 2 arranged side by side andhaving corresponding mumetal cores 3 and 4 which are joined together attheir lower ends. These cores extend upwards outside the coils and areconnected to corresponding fiat parallel munietal plates 5 and 6 whichconstitute the pole faces between which the armature of the relay rocks.The plates 5 and 6 are maintained a fixed distance apart by two uprightnon-magnetic bars 7 which are arranged between the plates 5 and 6 alongtheir adjacent vertical sides. The faces of the bars in contact with theplates are accurately finished so that the distance between the platesis accurately determined. The lower ends of the plates and the bars andthe extension of the cores 3 and 4 are held in position by two bolts 8,whilst two further bolts 9 hold in position the upper ends of the platesand the bars and also two brackets 10, upon the upper surface of whichis mounted an insulating disc 11, for example, of mycalex, that is amaterial containing flakes of mica with glass as the binding material.This disc 11 carries the contact arrangement of the relay. A bottomplate 12 is fixed across the bottom of the plates 5 and 6 and the bars7, so that the armature is completely enclosed with in a box made up ofthis bottom plate 12, the disc 11, the bars 7 and the plates 5 and 6.This particular design of relay thus substantially prevents magnetic orother particles from penetrating into regions near the armature.

The armature, which is pivoted between the centres of the two brass bars7 as described below, consists of a permanent magnet 15 of rectangularcross-section and two similar radiometal end pieces 16 secured to themagnet 15 at its poles, that is at the top and bottom.

The two radiometal end-pieces 16, which may be laminated, are secured tothe magnet 15 in one of several different ways. Thus powder metallurgytechniques may be utilised, by arranging within a mould the twomaterials in powder form, applying the necessary high pressure andfinally sintering the powders to form the composite armature, this thusbeing made in one piece.

In another method, the parts are secured together by dovetailing.

Another method of securing the parts together is by using an epoxy resinsuch as one of those sold under the trade name of Araldite, and yetanother method is using solder.

Again the pole-pieces may be clamped on the ends of the permanentmagnet, for example by means of nonmagnetic strips running down thesides of the armature and held by screws to the pole-pieces, the edgesof the strips being bent around the sides of the magnet.

The end pieces 16 have a greater thickness than the magnet, so that thedistance between each end piece and the plate 5 or 6 is correspondinglysmall, thus concentrating the polarising flux at the ends of thearmature. Because of the properties of radiometal, there is a very muchsmaller reluctance in the signals magnetic circuit than when permanentmagnet material alone is used as :23 the armature. Thus a very muchhigher degree of efficiency is obtained. Since the incrementalpermeability of radiometal decreases, however, as it approachessaturation, the parts of the magnetic structure which carry the majorpart of the polarising flux as well as the signals flux, that is the endpieces and the plates and 6, are made of sutficient cross-sectional areato keep the flux density to a low value so that the path traversed bythe signals flux has a satisfactorily high value of incrementalpermeability.

The polarising and signals magnetic circuits are shown in Figure 3. Theflux flowing through the polarising circuit is shown in full lines andis always in the direction shown, whilst the flux flowing through thesignals circuit is shown in dotted lines and its direction depends uponthat of the current in the signal coils l and 2.. it will be understoodthat the polarising flux will usually be many times as great as thesignals flux. It can be seen that when the signals flux is in thedirection indicated, the magnetic fields are strongest to the right ofthe top end-piece and to the left of the bottom end piece, and thiscauses the armature to rock in a clockwise direction. Reversal ofcurrent in the signals coils l and 2 will obviously cause the armatureto rock in the reverse direction. It will be noticed that any suchrocking changes only the lengths of the air gaps between the armatureand the plates 5 and 6, and does not alter their areas.

As can be seen most easily in Figures 4 and 5, two pins 17, fixed ontothe sides of the magnet 15 and acting as the pivot of the armature, areeach held within a corresponding sleeve 18 made of an elastomer such assilicone rubber, each sleeve being held within a metallic cylindricalholder 19 formed with a circular flange 263 at the end further from thearmature. Each elastomer sleeve 18 may be bonded to either the holder orto the pin or to both in order to prevent it slipping. In an alternativearrangement, shown in Figure 9, the end of each pin 17 is screw-threadedto cooperate with a nut 20a which maintains the sleeve 18 in position.Both these arrangements are in accordance with my co--pendingapplication Ser. No. 529,467, filed August 19, 1955. Instead of usingthis elastomer pivoting system, the armature may be mounted on springs,for example springs of the type described in my British patentspecification No. 734,352.

Each holder 19 is held within a corresponding bore 21 formed in one ofthe non-magnetic bars which thus serve both to determine the gap betweenthe plates 5 and 6 and to support the armature pivoting system. outerdiameter of each holder 19 is smaller than that of its bore 21 so that,until the holders 19 are clamped in position, the armature may beadjusted with respect to the plates 5 and 6. Each of the flanges 2t liesin a corresponding shallow groove 22 formed across the bar 7 and thesides of the two plates 5 and 6, this groove lying Within a deeper andlonger portion 23 also cut across the bar 7 and the sides of the plates5 and 6. The groove 22 is made only just slightly wider than the outerdiameter of the circular flange 20, so that the pivot of the armature isfixed in a vertical direction but. owing to the loose fit of the holder1% in its bore '31, it can be moved at right angles to this direction sothat the armature may be adjusted with respect to the plates 5 and 6.During the assembly of the relay, spacing shims (not shown) aretemporarily inserted between the arma ture and these plates 5, 6, theshims having a thickness to correspond to the required width of the airgaps, and the pivot 17 of the armature is then fixed by a nonmagneticplate 24 which fits into the cut-away portion 23 and which is fixed byscrews 24a onto the bar. Thus the centre portion of this plate 24, whichis formed with a small aperture 25 through which the pin 17 of thearmature may pass, presses against the flange 29 to maintain it in itscorrect position.

The

One of the pins 17 is longer than the other (see Figure l) and passesthrough the corresponding aperture 25. Thus a long upright magneticstrip 28, fixed to this longer pin 17 and extending from near the top ofthe signals coils 1, 2 to just above the disc 11, rocks to and fro withthe pin 17 and the armature and thereby serves to convey the rockingeffect of the armature to the contact-making arrangement on the disc 11.Lying on the strip 28, and held to it by its own flux is a permanaentmagnet in the form of a thin plate 29 which is pivoted freely about acylindrical boss 30 formed on the outer surface of the strip 28. Thisthin plate 29 serves to produce an inertia damping effect onoscillations of the armature in the manner disclosed in my Britishpatent specification No. 673,867. In order to bring about operation ofthe contacts, the strip 23 is turned over at the top through a rightangle so as to form a horizontal platform on which is secured abarrel-shaped insulating bead 31 which then rocks with the armature.

Two ears 32 which are fixed to and depend from a spring arm 33 extendingat right angles to the direction of movement of the bead 31 are spreadto engage the bead 31 on opposite sides. Thus rocking of the bead causesthe spring arm 33, together with a pair of conducting studs 34 formingthe moving relay contacts which it carries near the ears, to move in onedirection or the other depending upon the direction of rocking of thebead 31. The side contacts with which the moving contacts 34 cooperatelie, of course, on opposite sides of the spring arm 33 and are arrangedto provide a degree of friction damping to reduce contact chatter andoscillation on impact, as explained in British patent specification No.484,472. Thus each of these side contacts consists of a stud 35 mountedon a spring strip 36 which is fixed at one end to a rigid backing bar 37so that the strip 36 and the bar 3'7 lie roughly parallel to, but spacedfrom, each other. The free end of the strip 36 and the nearby end of thebar 37 are bent towards the arm 33, and a plug 33 having a front facewith a desired frictional characteristic is screwed through this bentpart of the backing bar so that the free end of the strip bears upon thefriction surface. Now when one of the studs 34 makes contact with one ofthe studs 35, the strip 36 is pushed towards the backing bar and g atthe same time the free end of the strip slides over the frictionsurface. The energy thus absorbed reduces any tendency to chatter or tooscillate of the studs. When the thin plate 29 is employed therebyproducing an inertia damping eifect as previously mentioned, the plugs33 may be dispensed with.

Each backing bar 37 is supported by :1 corresponding resilient stripconnected at one end to the back of the bar and at the other end to anupright post 46 which is mounted on the disc 11. Each strip 45 is turnedthrough a right angle and so fixed to the post that the backing bar 37is approximately parallel to one of the surfaces of the post 4-6 andpresses on the front of adjusting screw 47 which is screwed through thepost 46. Thus the positions of the studs 35 are controlled by theseadjusting screws.

It is important in relays generally, to ensure that the magnetic andmechanical dead centres of the central contact supporting structurecoincide. This is because these centres change with temperature (andalso with age) by different amounts and thus, unless they are initiallycoincident, large errors produced by the drift of the zero position ofthe central contact supporting structure are found. In order to enablethis coincidence of the two centres to be brought about, the spring arm33 is anchored at its fixed end in an upright post 50 mounted at theapex of a triangular horizontal plate 51 which is adjustably fitted ontothe plate 11. This adjustable fitting is brought about by a hexagonallyheaded screw 52 with a conical under-surface which acts as a pivot forthe plate, and two screws 53 and 54 the shank portions of which are ofsmaller diameter than that of the bores in the plate 51 through whichthey pass. Thus the whole plate 51 (carrying with it the spring arm 33and the studs 34) may be turned through a small angle about the screw 52with a suitable tool, the plate then being locked in position bytightening all three screws.

The arrangement just described enables the coincidence of the two deadcentres to be easily brought about during the assembly of the relay.First of all the spring arm 33 is raised from between the studs 35. Twopositioning contact screws (not shown) are then screwed intocorresponding screw-threaded holes 60 tapped in the upright posts 46below the axis of the adjusting screws 47, and just opposite the strip28. These positioning contact screws are screwed into the holes 60 untilthe signals current required for the strip 28 to move from the frontface of one of them to the front face of the other is the same as thatrequired for the reverse process, and the positioning contact screws areadvanced so as to make the movement of the armature as small aspracticable consistent with observing the neutrality of the bias. Thespring arm 33 is then lowered, and the plate 51, upon which it ismounted, is turned through such an angle that the neutrality of thearmature bias is unimpaired. The nut 52 and the screws 53 and 54 arethen tightened so that the mechanical dead-centre is fixed incoincidence with the magnetic dead-centre.

The second example of a relay constructed according to the invention, isillustrated mainly in Figures 7 and 8, and differs from the firstexample firstly in the position of the housing or box for the armaturerelative to the signals coils 1 and 2, and secondly in the arrangementfor conveying the rocking effect of the armature to the contactassembly. Thus the housing, which again consists of the plates and 6,the bars 7, the disc 11 and the bottom plate 12, is arranged between thetwo signals coils 1 and 2 so that this relay is shorter and fatter thanthat of the first example. The bead 31 is carried, not on the strip 28,but on a vertical metallic pin 65 fixed into the upper radiometal endpiece 16 of the armature, and projecting through a hole in the disc 11.The upper radiometal end piece 16 is formed with a hole to counteractthe efiect of the pin so that the centre of gravity of the armature lieson the pivotal axis of the armature. Instead of providing on the top ofthe pin 65 a bead made wholly of insulating material, a metallic ring(not shown), the outside surface of which forms part of a sphere, may bemounted on the pin 65, with an elastomer sleeve interposed between thepin and the ring. The flexibility which this elastomer sleeve introducesreduces distortion of the spring arm 33 should the ring be gripped sotightly as not to slide in the embrace of the cars 32.

When the pin 65 is used to convey the rocking effect of the armature tothe contact assembly, as described above, there is, of course, no needfor one of the pins 17 to be extended outside the armature box. However,if it is desired to employ inertia damping as before, to reduceoscillations of the armature, one of the pins 17 is so extended, andcarries a flat strip, not bent over at the top to form a platform as inthe form shown in Figures 1 and 2, and to this strip, a permanent magnetin the form of a thin plate is allowed to adhere as before.

Either of the relays described above may easily be converted into a oneside stable relay by forming a threaded hole in one of the plates 5 and6 near one of the radiometal end pieces and employing an externallythreaded plug within this hole to effect adjustments in the stability.The unsymmetrical stability may be in creased by providing a furtherhole and plug in the other plate opposite the other end piece.

I claim:

1. A polarised electromagnetic device comprising, a signal windinghaving a core, a magnetic structure connected to the ends of said coreand providing two parallel paths for signal flux, each path includingopposed stationary pole faces between which signal flux flows, the twomagnetic paths being spaced apart in a direction normal to the directionof flux flow between the pole faces of each path, an elongated armaturehaving a magnetically soft end portion located between the pole faces inone magnetic path and another magnetically soft end portion locatedbetween the pole faces in the other magnetic path, means mounting saidarmature for pivotal movement about an axis located between said fluxpaths, whereby, as said armature moves, said end portions approach andrecede from said pole faces to alter the lengths of the gaps betweensaid pole faces and said end portions, as measured normal to said polefaces, and a permanent magnet interposed between said end portions ofsaid armature and establishing polarising flux flow through the said endportions in series.

2. A polarised device according to claim 1, wherein said magneticstructure including a pair of pole pieces connected magnetically to saidcore and each having a flat surface constituting the pole faces on oneside of said armature, said flat surfaces being parallel both to oneanother and to the facing surfaces of said soft-iron end portions, whensaid armature lies in a symmetrical position between said pole faces.

3. A device according to claim 1, wherein said polarising magnet is apermanent magnet, and the distance between each of said pole faces andthe facing surfaces of said end pieces being less, when the armaturelies in a symmetrical position between said pole faces, than thedistance between the said magnet and the nearest part of the saidmagnetic structure.

4. A polarised device according to claim 1, wherein said permanentmagnet is embodied in said armature and said soft-iron end portions aresecured to said magnet at its ends to make up the whole of saidarmature.

5. A polarised device according to claim 1, wherein the whole of saidarmature comprises a sintered structure.

6. A polarised device according to claim 1, wherein said magneticstructure including a pair of pole pieces formed with surfacesconstituting the opposed stationary pole faces of both of said magneticpaths, said pole pieces being spaced from one another by two parallelnonmagnetic spacing members which, together with the pole pieces,constitute the major portion of a housing in which the armature issubstantially completely enclosed.

7. A polarised device according to claim 6 wherein a movable part ofsaid armature extends out of said housing and including a contactassembly mounted on said housing in a position to be operated by saidmovable part.

8. A polarised device according to claim 7, and including an arm fixedoutside said housing to the pivot of said armature so as to rock withit, said arm controlling said contact assembly.

9. A polarised device according to claim 8, and including acontact-supporting piece which constitutes part of said housing, andsaid contact assembly comprises a rigid member adjustably mounted onsaid contact supporting piece, a resilient strip carried by said rigidmember and movable with it, a pair of movable contacts carried by saidstrip and having a position controlled by said arm, and a pair of sidecontacts arranged for cooperation with said movable contacts.

10. A polarised device according to claim 9, wherein said rigid memberis pivoted on said contact supporting piece so as to enable said movingcontacts to be moved relatively to the side contacts, whereby themechanical and magnetic dead centers of the contact assembly may be madecoincident.

11. A polarised device according to claim 1, wherein said magneticstructure including a pair of pole pieces formed with surfacesconstituting said pole faces of both of said air-gaps, said pole piecesbeing spaced from one another by two parallel non-magnetic spacingmembers which serve as supports for the armature pivoting system.

12. A polarised device according to claim 1, and including resilientmeans acting on said armature to oppose the forces due to saidpolarising magnet, said resilient means being adjustable relatively tosaid pole faces so that the positions of zero mechanical and zeromagnetic force acting on said armature may be brought into coincidence.

13. A polarised device according to claim 12, and including a pivotallymounted plate, said resilient means being mounted on said plate andbeing adjusted as said plate is turned, and means for clamping saidplate in the adjusted position.

References Cited in the file of this patent UNITED STATES PATENTSBurrows Feb. 3, 1920 Broughton Ian. 10, 1933 Bengtsson Jan. 19, 1954Distin Apr. 10, 1956 FOREIGN PATENTS Great Britain June 29, 194

France June 30, 1954

